In the aforesaid applications and patent, there is disclosed an apparatus for in vivo separation of plasma from blood utilizing at least one elongated microporous fiber having a hollow interior for being received within a blood vessel without significantly obstructing fluid flow through the vessel. The fiber or fibers comprise a material having a porous size sufficient to allow plasma to diffuse through the pores into the hollow fiber interior but which pores prevent cellular components larger than plasma to diffuse or enter the fiber interior. The elongated fiber or fibers are in fluid communication with a catheter, preferably a dual lumen catheter having a first tube which permits passage of the plasma from the fiber, and a second hollow tube which returns plasma to the blood vessel. Various systems, apparatus and methods for use of the aforesaid fiber technology including measurement of blood parameters, kidney dialysis, and separation and removal of a substantial number of materials are disclosed. The disclosure of the aforesaid fibers, the systems and methods of use in the aforesaid applications and patent are incorporated herein by reference.
In the aforesaid patent and applications, the portion of the apparatus and systems comprising the fiber or fibers implanted in a blood vessel are illustrated as extending somewhat loosely and non-uniformly or randomly lengthwise, generally parallel with the direction of blood flow in the vessel or vein. According to the present invention, it has been found that such a fiber disposition is not the most efficient for achieving relatively high or preferred plasma diffusion rates. It is to the improvement of such fiber elements or devices and apparatus design that the present invention is directed.